Hi Barry,
Thanks so much for reaching out!
When managing orders/attendees there are a number of considerations to take into account, one of them being manually increasing ticket stock, if desired, to ensure that the proper number of tickets still are available.
You can read more about managing orders and tickets here:
https://theeventscalendar.com/knowledgebase/refund-cancel-tickets-order/
One thing you can do is to alter the total_sales custom field on the WooCommerce Product page that is associated with the ticket that you are trying to edit. You can change that number to reflect the actual number of attendees that you have, which will then change what you see in your Attendees tab.
You can also alter the ticket stock on the Edit Event page, where you edit your ticket.
Let me know how that goes and if you have any other questions on this topic!
Thanks,
Jaime